1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a semiconductor device including a termination structure, and a method for fabricating such a semiconductor device.
2. Description of the Background Art
Power devices are semiconductor elements mainly intended for electric equipment for use in power conversion or power control, and allow for higher breakdown voltages and larger currents than in typical semiconductor devices. Power devices need to sustain a high voltage by cutting off current when a reverse voltage is applied thereto. In order for power devices to withstand higher breakdown voltages, “Handbook of Power Device & Power IC” edited by The Investigation Committee on High-Performance and High-Functionality Power Device & Power IC, The Institute of Electrical Engineers of Japan, and published by Corona Inc. (pp. 54-64 and 170-174) discloses a FLR (Field Limiting Ring) structure and a termination structure such as a field plate structure.
In the FLR structure, a main junction between an N-type impurity region of low concentration and a P-type impurity region located at an internal surface of this N-type impurity region is surrounded by a plurality of ring-shaped P-type impurity regions. With this structure, when a reverse voltage is applied, junctions formed by the respective ring-shaped P-type impurity regions sequentially produce punch-through before the main junction punches through, thereby reducing the electric field of the main junction.
Further, Japanese Patent Laying-Open No. 2002-231944 and Japanese Patent Laying-Open No. 05-190693, for example, disclose a structure including a ring-shaped conductive film provided on each FLR with an insulation film interposed therebetween. With this structure, the conductive films function as equipotential rings, thereby mitigating the influence of movable ions contained in the insulation film.